Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$206.96	6.860%	$221.1575	$221.16	$221.15	$221.20
Purchase #2	$81.80	10.741%	$90.5861	$90.59	$90.60	$90.60
Purchase #3	$180.66	7.653%	$194.4859	$194.49	$194.50	$194.50
Purchase #4	$231.41	4.197%	$241.1223	$241.12	$241.10	$241.10
Purchase #5	$102.96	3.269%	$106.3258	$106.33	$106.35	$106.30
Purchase #6	$221.67	6.324%	$235.6884	$235.69	$235.70	$235.70
Purchase #7	$130.56	10.674%	$144.496	$144.50	$144.50	$144.50
7 purchase totals =	$1,156.02		$1,233.8620	$1,233.88	$1,233.90	$1,233.90